Schizomycetes. 5 



It is in part quite impossible, especially in the genera 

 Micrococcus and Bacterium, to indicate morphological 

 distinctions between the species. We are in these cases 

 confined exclusively to physiological distinctions \ we employ 

 diiferences in chemical action for the limitation of species. 

 The Schizomycetes, as has been already stated, excite 

 peculiar decompositions in their substratum ; they transform 

 complicated chemical combinations into simpler ones. This 

 chemical action consists (i) in the production and excretion 

 of colouring matters ; (2) in the exciting of various fermen- 

 tations ; and (3) in the decomposition of the humours of 

 animal and human bodies, whereby diseases arise. We 

 distinguish, therefore, (i) chromogenous, (2) zymogenous, and 

 (3) pathogenous species respectively. 



But especially in relation to those forms which belong 

 to the two last subdivisions does the greatest uncertainty 

 reign. Nay, in regard to the pathogenous Schizomycetes 

 such untrustworthy, even foolish, assertions and so-called 

 observations have been published, that only the greatest 

 foresight can guard against errors.* 



There is left, therefore, especially for the systematist, 

 nothing but to accept Cohn's conscientious researches, 

 provisionally to adopt his classification and nomenclature as 

 the only one which is founded upon botanical principles, and 

 to add to it only what has been discovered by trustworthy 

 investigations. The nonsense which Hallier and Co. have 

 tried to introduce into the science naturally remains un- 

 regarded. 



• This arises chiefly from the fact that many medical men, who have 

 tried to investigate these things, have been totally unskilled in the use 

 of the microscope, at any rate with high powers, and have often also 

 been untrained in the methods of observation. An eminent physician of 

 the United States, Dr. Schmidt, solemnly asserted that the Bacillus 

 tubtrculosis of Koch was only a fat-crystal !— Tr. 



